By Chris Hogg
BBC News, Taipei
There was a noisy protest by taxi drivers in the centre of Taipei as demonstrators began to gather around the city.
Protestors hold banners and display a mock model of missiles
Ten different routes had been organised and they came from all across this island to add their voice to the protest, hundreds of thousands of people.
By the time the 10 different marches converged on the square in front of the presidential palace, the roads were blocked as far as the eye could see.
There was a crush on the wide boulevard in front of the palace. But there was no panic, no angry confrontations.
The anger there was here, was directed at the Chinese leaders on the mainland. The rhetoric on the signs and banners the protestors carried was to the point.
"Peking Duck off" was one of the most striking.
Those I talked to along the route were ordinary people, many of them students, house wives and pensioners, not necessarily political activists.
But once they saw my microphone many would rush over to share with me their opinions.
"We feel threatened," one man told me. "China's new law is an attempt to bully us," said another.
Ruled by separate governments since end of Chinese civil war in 1949
China considers the island part of its territory
China has offered a "one country, two systems" solution, like Hong Kong
Most people in Taiwan support status quo
A woman protester told me of her concern that now China had a new law to use non-peaceful means towards Taiwan if the island moves toward independence, the die had been cast.
"What happens if a more extreme faction takes over in Beijing," she said. "Then we'd be done for."
But this was not a people subdued. We shall overcome, they sang.
At the climax of the rally, President Chen Shui-bian joined march organisers on stage. Not to give a speech admonishing Beijing as it turned out, but to sing with the crowd and to encourage them.
His advisers clearly thought angry rhetoric from the man in charge would enflame what are already poor relations with China.
So how will Beijing react to this show of defiance from this small island it regards as nothing more than a breakaway province, which should be reunited with the mainland, by force if necessary.
I asked one senior legislator I met in the crowd if it was dangerous to provoke the Chinese leadership in this way?
"Nothing we do pleases them," she said, "so why should we care."
The purpose of the rally, the organisers said, had been to remind the international community that Taiwan had a grievance. The massive turnout meant the message was loud and clear and hard to ignore.